[LEAPSECS] IERS Message No. 180: Revision of IERS Earth Rotation Series effective 1 February 2011

Steve Allen sla at ucolick.org
Wed Jan 5 15:09:34 EST 2011

On Wed 2011-01-05T19:42:58 +0000, Poul-Henning Kamp hath writ:

> TAI is supposed to be a "uniform atomic timescale"

Not really. TAI is supposed to be as uniform as possible
given the inputs which are available on a monthly basis.
TAI does not pretend to *be* uniform, only to timely try.

What time it is can never be known now. It is only possible to buy a
good enough clock, regularly compare it with some better clock, and
later do the table lookup to find out what time it was. The
algorithms involved in the table lookup are always subject to revision
by their implementors. So whereas the value of TAI for a given event
will never be changed, your ability to decide what value of TAI
corresponded to your timestamp is something you may want to revise.

to be fully general,
global substitute "your clock" and "TAI" with any clock and time scale.

Steve Allen <sla at ucolick.org> WGS-84 (GPS)
UCO/Lick Observatory Natural Sciences II, Room 165 Lat +36.99855
University of California Voice: +1 831 459 3046 Lng -122.06015
Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m

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